Polyamide filaments

ABSTRACT

A linear terpolyamide derived from 80 percent by weight of hexamethylene diammonium adipate, 10 percent by weight of caprolactam and 10 percent by weight of hexamethylene diammonium isophthalate is especially useful for melt spinning into a sideby-side conjugate filament in which the other component is preferably polyhexamethylene adipamide. In order to obtain a satisfactory crimp permanence and hot water retraction, the filament, after drawing, is heat relaxed at a relax ratio greater than 1.3. A monofilament yarn has particular application in the manufacture of stockings.

United States Patent 1 Pacini et al.

1151 3,675,408 [451 July 11,1972

POLYAMIDE FILAMENTS Inventors: Bur-no Mardo Pecinl; Desnond Alli-ed Price; Anll Chandnlrant Parlkh, all of Pontypool, England Assignee: Imperial Chemical Industries Umlted,

London, England Filed: Deal], 1969 Appl. No.: 889,455

us. c1........................s7/14o Bx, 161/173, 260/78 L, 264/210 F, l6l/l77 m. (:1. "002; 3/02 FlelrlolSeareh ..l6l/l73, 175,177; 260/78L; 264/!71; 57/140 BY Relerenoes Cited UNITED STATES PATENTS 5/1967 Cool: et L 3,526,571 9/!970 Ogata ..l6l/l75 Primary Examiner-Robert F. Burnett Arm/an: xaminerlinda Koeckert Attorney-Leonard Horn and Stephen D. Murphy [57] ABSTRACT A linear terpolyamide derived from 80 percent by weight of hexamethylene diammonium adipate, l0 percent by weight of caprolactam and l0 percent by weight of hexamethylene diammonium isophthalate is especially useful for melt spinning into a side-by-side conjugate filament in which the other component is preferably polyhexamethylene adiparnide. In order to obtain a satisfactory crimp permanence and hot water retraction, the filament, after drawing, is heat relaxed at a relax ratio greater than L3. A monofilament yarn has particular application in the manufacture of stockings.

POLYAMIDE FILAMENTS The present invention relates to improvements in polyamides which may be employed as one component in the manufacture of polyamide conjugate filaments, that is filaments comprising two different polyarnide components existing in a contiguous relationship throughout the length of the filament.

Conjugate filament yarns, which may comprise one or more of the said filaments, in which the filament components exist in an eccentric relationship, either side-by-side or sheath/core, are known to possess a spontaneous or potential crimp thus not requiring mechanical processing. Such yarns have obvious advantages but the nature of the crimp has proved difficult to control.

A conjugate filament yarn intended for use in, say, hosiery should preferably have a high hot water retraction (R,,.) and a high crimp permanence (CP). The former reflects the amount of bulk which will be developed in the fabric and the latter the recoverable stretch. These parameters are especially important in stretch fabrics and especially in stretch stockings; poor bulk will, in these fabrics, result in a low degree of stretch and low crimp permanence will result in distortion of the fabric which, in the case of stockings, is evidenced by "bagging at the knees, for example.

Frequently high crimp permanence is achieved only at the expense of a low hot water retraction and at best the result is a compromise.

We have now found that if a ternary copolymer derived from at least 80 percent and less than 90 percent of hexamethylene diammonium adipate, and at least 5 percent by weight of each hexamethylene diammonium isophthalate and epsilon caprolactam is used as one component of a conjugate filament in which the other component is a homopolyamide, a filament having improved crimp permanence and hot water retraction is obtained. The conjugate filament spun from these components, should subsequently be drawn and heat relaxed. A drawn and relaxed 20 denier monofilament will preferably have a hot water retraction of at least 30 percent and a crimp permanence of at least 45 percent. Accordingly, therefore, from one aspect the present invention provides a linear terpolyamide derived from at least 80 and less than 90 percent by weight of hexamethylene diammonium adipate and at least 5 percent of caprolactam or amino caprioc acid and at least 5 percent by weight of hexamethylene diammonium isophthalate.

The preferred ratio by weight of the three components in the copolyrner is 80/10/10 respectively.

From another aspect, the present invention further provides a conjugate filament comprising as one component the terpolyamide defined above and as the other component a homopolyamide.

The homopolyamide is preferably polyhexamethylene adipamide and the two components are preferably in a highly eccentric side-by-side relationship; e.g., the filaments should preferably comprise equal proportions by weight of the ter polyamide and homopolyamide components.

The invention further includes a multifilament yarn comprising two or more of the above defined conjugate filaments.

Crimp permanence is determined in the following manner. A filament is immersed in boiling water for a period of minutes under a stress (in air) of 2.5 mg/denier (mg/d.) and subsequently conditioned at 65 percent relative humidity and 70 C for 1 hour under the same load. A 10 cm. length is clamped in an lnstron textile tester under the same load and extended at a rate of 10 ems/sec. to a stress of 1 g/d and held under this load for 30 secs. The load extension curve obtained is designated A in FIG. 1. The filament is then retracted to a l0 cm. clamp displacement and reclamped to a l0 cm. length maintaining the 2.5 mg/d. load. The filament is then again extended at 10 ems/secs. to l gm/d., and retracted immediately to the 10 cm. clamp displacement. The load extension curve obtained is designated B in FIG. 1. Crimp permanence is then defined as the extension under a load of 0.33 gms/d. at curve B divided by the extension at the same load at curve A X 100, Le, (by/0x) X 100 percent.

The hot water retraction (11,) is determined by wrapping a sufficient number of turns of the test filament on a wrap wheel such that the filament denier multiplied by the number of wraps equals 6,000. The wrapping tension should be less than 0.5 g/d. A 10 g. weight is hung on the loop of the skein corresponding to a filament stress of 0.00087 g/d. The skein loaded with the 10 gm. weight is immersed in water at 60 C for a period of 2 minutes and the skein length L in inches measured in the water. If the circumference of the wrap wheel is l9 inches, the retraction is defined as:

As a guide to yarn contractive power, the stocking panel length (S.P.L.) was measured for the yarns of examples 2 8.

Stocking Panel length (S.P.L.) is measured by knitting a yarn on a conventional single feed stocking machine into a stocking of standard volumetric size using the same stretch length in the test for the ankle, panel and thigh portions. The stocking is placed on a standard 8% inches boarding form in a relaxed and wrinkle-free position, and the distance from the sole side of the heel to the end of the panel measured.

Stockings made from yarns having an S.P.L. in excess of 20 inches proved to be unacceptable.

In order to obtain the required crimp permanence and hot water retraction properties it is preferred that the crimp in the conjugate filaments be developed by a heat relaxing treatment under substantially zero tension immediately after drawing.

The aforementioned heat relaxing treatment is preferably carried out by forwarding the freshly drawn yarn to a heat relaxing zone by means of a jet of heated gaseous fluid, such as one at a temperature desirably not less than 150 C. After leaving the relaxing zone the crimped yarn is forwarded by a roll, (relax roll), and associated nip roll to some conventional wind-up system, e.g., ring and traveller. A preferred embodiment of this process will now be described with reference to the accompanying drawings.

1n the drawings:

FIG. 1 is a load extension curve,

FIG. 2 is a schematic arrangement for drawing, relaxing and winding a conjugate filament yarn and FIG. 3 is a more detailed diagrammatic representation of the forwarding jet and relaxing tube.

Referring to the drawings, a yarn l is taken from a supply package 2 passed round feed roll 3, pin snubbing 4 and draw roll 5 to draw the yarn to the required extent. From the draw roll the yarn passes to the forwarding jet 6 and relaxing tube 7. The yarn enters the forwarding jet via entry tube 12 and then passes into jet 13. A heated gaseous fluid enters through inlet 14 and carries the yarn through the jet 13 into the relaxing tube 7 where the yarn assumes a crimped configuration. On leaving the bottom of the relaxing tube the yarn passes between relax roll 8 and associated nip roll 9 and is forwarded to bobbin 11 on which it is wound up by a conventional ring and traveller system. The presence of the nip roll 9 is essential to prevent the balloon tension in the yarn being wound on the bobbin running back into the relaxing tube.

The ratio of the speed of the draw roll to the speed of the relax roll is the relax ratio (RR) which is preferably greater than 1.3 and more preferably at least 1.5.

The following examples illustrate the invention EXAMPLE 1.

A copolymer derived from hexamethylene diammonium adipate, epsilon caprolactam and hexamethylene diammonium isophthalate in the ratios 10:10 parts by weight is spun as one component as a side-by-side conjugate monofilament having equal proportions by weight of the components, the other component being polyhexamethylene adipamide. The spun yarn had a denier of and was drawn at a draw ratio of 4.80 at 2,000 feet/minute and subsequently relaxed by the process described above using hot air as the gaseous fluid. The yarn was finally wound up on a bobbin rotating at 8,000 rpm. under a tension of 4 8 gms. weight.

TABLE Relax Ratio Air Temperature C.P. R Yarn (RR) Example i l.70 205 63 37 66/66z6 1.55 240 Si 29 66/66z6 i? 2.25 220 39 45 The air temperature quoted above is measured one-half inch above the entry point of the yarn into the relax tube 7 of FIG. 3.

In the following examples. the polymers of Example 1 were spun into side-by-side conjugate filaments comprising equal proportions by weight of each component having a spun denier of 85. and wound up on a bobbin at L068 feet/minute. Details of the drawing and relaxing processes of the yarn and stocking properties are given in Table 2.

EXAMPLE 8.

In this example the weight ratio of components in the terpolymer was 90:5:5 parts by weight of hexamethylene diammonium adipate, epsilon caprolactam and hexamethylene diammonium isophthalate. The polymer was spun into a yarn and wound up under the conditions described in the previous examples. Details of the draw relaxing process yarn and stocking properties are given in Table 3.

TABLE 3 EXAMPLE 8 Draw/relaxing Draw roll speed l".p.m. 2000 Draw ratio 4.80 Relax ratio 1.50 Relax temp. "C 225 Draw pin temp. C 72 Spindle speed r.p.ml 7980 Yarn Properties R 20.4 CP% 86.4 Stocking Properties S.P.L. (inches) 22 What we claim is: j l. A side-by-side conjugate filament having improved crimp permanence comprising as one component, a linear terpolyamide derived from at least and less than percent by weight of hexarnethylene diammonium adipate, at least 5 percent of caprolactam or amino caproic acid and at least 5 percent by weight of hexamethylene diammonium isophthalate and as the other component of said conjugate filament, a homopolyamide.

2. A conjugate filament according to claim 1 wherein said homopolyamide is polyhexamethylene adipamide.

3. A conjugate filament according to claim 2 wherein said components exist in a highly eccentric relationship.

4. A conjugate filament according to claim 3 comprising equal proportions by weight of the terpolyamide and homopolyamide components.

5. A conjugate filament according to claim 4 being a monofilament having a retraction in water of at least 30 percent and a crimp permanence of at least 45 percent.

6. A multifilament yarn comprising two or more of the conjugate filaments of claim 1. 

2. A conjugate filament according to claim 1 wherein said homopolyamide is polyhexamethylene adipamide.
 3. A conjugate filament according to claim 2 wherein said components exist in a highly eccentric relationship.
 4. A conjugate filament according to claim 3 comprising equal proportions by weight of the terpolyamide and homopolyamide components.
 5. A conjugate filament according to claim 4 being a monofilament having a retraction in water of at least 30 percent and a crimp permanence of at least 45 percent.
 6. A multifilament yarn comprising two or more of the conjugate filaments of claim
 1. 